Unravel the Catalytic Effect of Two-Dimensional Metal Sulfides on Polysulfide Conversions for Lithium-Sulfur Batteries.

Despite extensive studies, the role of polar chemical interfaces on carrier materials anchoring polysulfide species remains an ambiguous but intriguing topic for lithium-sulfur batteries. Herein, to further investigate the effect of metal sulfides in the conversion of polysulfides, three kinds of MxSy (M = Cr, Mo, and W) are chosen and prepared in the forms of two-dimensional MxSy/C composites via a method using NaCl as a template and a subsequent high-temperature sulfuration process. Compared with a blank sample, the three composites exhibit superior adsorption of soluble polysulfides and faster kinetics of the deposition of Li2S2/Li2S, especially on Cr3S4/C and WS2/C. These differences in performances of the three composites are further evaluated by the values of the Gibbs free energy in each step of polysulfide conversion. In the conversion processes of Li2S4 to Li2S2 and then to Li2S, the values are more negative on Cr3S4 and WS2, showing stronger promotion abilities for the formation of Li2S than MoS2. This work can effectively deepen the role of metal sulfides in the conversion process of polysulfides and provide valuable insights into the design of superior carriers for lithium-sulfur batteries.